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Dive into the research topics where François Sidoroff is active.

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Featured researches published by François Sidoroff.


European Journal of Mechanics A-solids | 2000

Elastic-plastic homogenization for layered composites

A. El Omri; A. Fennan; François Sidoroff; A. Hihi

A general method for the homogenization of rigid plastic or elastic-plastic layered structures is proposed. This method is based on a hybrid formulation of the constitutive equation for each phase, thus reducing the homogenization procedure to a simple mixture law. This non-classical hybrid formulation is obtained for both the rigid-plastic and elastic-plastic models. The resulting homogenized behaviour is then illustrated by some examples with special emphasis on the resulting anisontropy and in particular on the off-axis tensile behaviour.


Composites Science and Technology | 2000

Quantitative analysis of the micro-indentation behaviour of fibre-reinforced composites: development and validation of an analytical model

M. Zidi; Luc Carpentier; A. Chateauminois; François Sidoroff

Abstract A shear-lag model has been developed in order to assess interfacial shear strength from micro-indentation experiments. The treatment of the experimental load/displacement curves is based upon the quantification of the two components of the indenter displacement, i.e. (i) the elasto-plastic indentation of the fibre surface by the Vickers indenter, and (ii) the displacement of the fibre surface due to its compression and to the deflection of the matrix. The latter component has been modelled by using an analytical shear-lag model which takes into account both fibre/matrix debonding and fibre sliding in the debonded areas. Some of the basic hypothesis of this analytical approach have been checked by finite-element (FE) simulations with appropriate model configurations. By means of this model, the critical shear debonding stress can be obtained from the experimental indentation curves. Moreover, the data-reduction scheme takes into account separately the local environment of each indented fibre. This method has been successfully applied to experimental data by using a unidirectional E-glass/epoxy composite.


Composites Science and Technology | 2001

Development of a micro-indentation model simulating different mechanical responses of the fibre/matrix interface

M. Zidi; Luc Carpentier; A. Chateauminois; Ph. Kapsa; François Sidoroff

An analytical shear-lag model has been developed for quantifying the interfacial shear strength of glass-reinforced composites from micro-indentation experiments. The model takes into account the local fibre environment, together with the occurrence of debonding and fibre sliding. In order to simulate the experimental indentation curves, various interfacial laws have been implemented. In a first approach, it was assumed that the shear stress in the debonded part of the interface was constant and proportional to the debonding stress. A more refined generalised interface law relating the shear stress to the fibre displacement was subsequently introduced to describe a progressive transition from an adhesive to a sliding state. The model has been successfully applied to the analysis of experimental reduced indentation curves giving the displacement of the fibre surface as a function of the applied load.


Tribology and Interface Engineering Series | 1996

Particulate and granular simulation of the third body behaviour

A. Ghaouti; Marie Chaze; Philippe Dubujet; François Sidoroff

Intermediate between molecular dynamics and granular mechanics, particle mechanics is based on a direct numerical simulation of the quasi-static behaviour of a particulate aggregate with molecular type interaction laws. Two different types of simulations are presented with special emphasis on the post processing analysis. For application to friction and wear, these methods are exemplified on the two dimensional monotonous and cyclic shear behaviour of an amorphous third body layer between crystalline first and second bodies. Influence of the third body thickness, normal load and loading conditions are discussed.


European Journal of Mechanics A-solids | 1999

Material compressibility effects for the squeeze of very thin films

François Auslender; Mohammed Trifa; François Sidoroff

Abstract The purpose of the present work is the study and clarification of the essential role played by the material compressibility of very thin solid layers such as for instance appear in surface force experiments. For the sake of simplicity, attention will be focused on an elastic film squeezed between rigid surfaces. The starting point is the classical lubrication theory reformulated within the framework of linear elasticity (Incompressible Reynolds Model). This model is then extended to include compressibility effects. This extension is based on a phenomenological analysis of the stress and strain fields obtained in some simple model cases and which are shown to correspond to an oedometric squeeze inside the contact with boundary corrections. This results in the oedometric Reynolds model which is then applied to two special cases: a uniform film of constant thickness under plane strain condition and the interfacial film occurring in the sphere/plane contact. These two problems confirm the fact that compressibility cannot be neglected for very thin films and show that the governing adimensional parameters combine compressibility and thinness.


Philosophical Magazine | 1996

Mechanical characterization of carbon–epoxy and glass–epoxy composites by indentation testing

Luc Carpentier; Philippe Kapsa; Jean Sarete; Mondher Zidi; François Sidoroff

Abstract The indentation technique has been developed to perform surface mechanical characterization of materials. This technique consists in monitoring the penetration of a diamond indenter in the material to be characterized while the displacement and the force are continuously measured. Modelling loading and unloading curves allows estimation of plastic and elastic properties of the material. Linking this technique with an optical sighting system permits the characterization of various phases of the composite materials with a displacement accuracy better than 0·1 μm. The mechanical behaviour of carbon or glass fibre reinforced polymer under various solicitations is mainly related to the behaviour of its ‘phases’: the matrix, the fibres and the fibre–matrix interface. Several techniques have been developed giving information about mechanical properties of the composite, particularly for the interfacial strength. Modelling static and dynamic indentation curves on fibres allows computation of the interfac...


International Journal of Engineering Science | 2002

Nanorheological analysis of the sphere plane contact problem with interfacial films

M Trifa; F Auslender; François Sidoroff

The contact between an elastic sphere and plane separated by an elastic interfacial thin layer is analysed under pure squeeze action. This analysis is an important step in the investigation of more realistic problem such as viscoelastic and heterogeneous squeeze problem encountered in surface force experiments. The problem is shown to be governed by two dimensionless parameters coupling the material properties of the layer (shear and bulk modulus) and the substrate (reduced young modulus) with the thinness ratio of the sphere plane distance to the sphere radius. Different regimes are obtained and described according to the value of these two parameters.


Composite Structures | 2000

Secondary effects in the analysis of the post-buckling bending test

I. Kallel-Kamoun; A. Chateauminois; François Sidoroff

The post-buckling bending test can be used as an alternate to the classical three-point bending test for the mechanical characterisation of fibre-reinforced polymer composites. Its main interest is the avoidance of localised contact stress below the loading nose, which often induce the premature failure of the specimens under three-point bending conditions. The derivation of strength and modulus values from this test is based upon a mechanical analysis, which is usually developed within the frame of the classical buckling analysis. This approach is based upon some assumptions, which have been justified in the real physical situation. The validity of the beam approximation has especially been discussed for the usual specimen geometry. In addition, the correcting factors due to membrane effects and the contribution of the rigid specimen grips are considered within the frame of the beam-bending problem.


Tribology and Interface Engineering Series | 1999

Elastohydrodynamic squeeze of thin films for the sphere-plane contact

M. Trifa; François Sidoroff; J.M. Georges

Abstract The elastohydrodynamic squeeze of thin films in a sphere-plane contact is analysed under imposed harmonic vertical displacement. A general model is presented taking into account - the viscoelastic rheology of the film, either homogeneous or heterogeneous - the film compressibility - the substrate elasticity. The model case of elasticity then allows the influence of the material properties to be analysed which appears coupled with the thinness ratio D/R. A complete analysis of the case of a viscous compressible fluid is then presented. The solution depends on two adimensional parameters coupling the material properties with the thinness ratio. Three different regimes are identified : hydrodynamic, elastohydrodynamic and mixed. As a conclusion, applications and extensions of these results will be discussed.


Revue Européenne des Éléments Finis | 1999

Un algorithme de calcul de structures élastoplastiques pour l'identification des lois de comportement des matériaux

Hédi Bel Hadj Salah; François Sidoroff; Abdehwaheb Dogui

Non homogenous tests are successfully used to identify constitutive models of material behaviour. Finite elements methods can be considered to analyse these tests. This paper presents a finite elements algorithm solving a non-linear elastoplastic problem without use of the well-known tangent matrix. Thus the computation of the plastic and elastic part are almost completely uncoupled. The proposed algorithm is well adapted to the identification of constitutive model. As an example, the Lankford coefficient, for a transversal isotropic model, is identified combining the plane tensile test and our algorithm.

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J.M. Georges

École centrale de Lyon

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M. Zidi

École Normale Supérieure

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Marie Chaze

École centrale de Lyon

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Ph. Kapsa

École centrale de Lyon

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A. Dogui

École centrale de Lyon

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A. Ghaouti

École centrale de Lyon

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